The present invention pertains to packaging for storage cylinders designed for storing compressed gases, and in particular an apparatus and method for packaging cylinders containing compressed oxygen.
In the handling of compressed gases stored in vessels such as cylinders, it is known that exposure of the cylinders to heat and increased temperatures may cause the pressure inside the cylinder to increase. It is also known to provide a pressure-relief mechanism that will open to vent the gas to the surrounding environment, if the pressure within the cylinder reaches levels that may be detrimental to the cylinder.
There are instances, however, where it is advantageous to delay the operation of the pressure-relief mechanism to prevent the contents of the cylinder from being released. One such instance involves the transportation of compressed oxygen cylinders in cargo holds. If the cargo hold is provided with flame retardant walls and is sealed, the fire may smolder or suffocate before causing any serious damage. In such a situation, it would be disadvantageous to allow the oxygen inside the cylinders to release into the area surrounding the cylinders because the oxygen may worsen the fire. Other instances where the present invention would be advantageous would include the shipment of toxic gases in cylinders in cargo holds.
For shipping cylinders containing compressed oxygen it has been known to provide an outer packaging or overpack to protect the cylinders from reaching temperatures that may trigger the pressure-relief mechanism.
It has been determined that the ATA 300 provides a significant amount of thermal protection to a cylinder exposed to a high temperature environment.
The ATA 300 is an overpack or outer packaging commonly used by airlines to transport their oxygen cylinders (ATA specification No. 300, Packaging of Airline Supplies, Category I). An ATA Specification No. 300 Category I (ATA 300) overpack or outer packaging is a resilient, durable overpack intended to be reused for a minimum of 100 round trips.
The ATA 300 cases have several drawbacks including their size and weight. The cases are rigid and bulky, and they are expensive. Also, because of the expense and durability of the cases, they have to be returned to their owner after each use. Accordingly, there is a need for a more economical, single use overpack that extends the time before a pressure relief mechanism on a compressed oxygen cylinder is triggered when the cylinder is exposed to elevated temperatures and that provides thermal protection comparable to the ATA 300.
The present invention meets the above-described need by providing a single use overpack and a method for packing a compressed gas cylinder in an overpack, that provides thermal protection that is the same as or better than the ATA 300, but is more economical to use and to manufacture.
The present invention provides a first container having openings at opposite ends and capable of being sealed by foldable flaps. The first container receives a cylinder with a valve. The cylinder contains a compressed gas and is equipped with a pressure relief mechanism for releasing the gas when the pressure inside the cylinder approaches a pressure detrimental to the cylinder. The cylinder and valve are typically enclosed in a protective bag. The bottom of the cylinder is provided with a bottom ring that conforms to the shape of the cylinder to prevent the cylinder from moving inside the first container. At the opposite end, a head ring is disposed around the top of the cylinder and around the valve. The head ring also prevents the cylinder from moving inside the first container and protects the valve from contact with the end of the container or the side walls of the container such that the valve is not inadvertently actuated or damaged during transportation.
Once the cylinder equipped with the head ring is placed in the first container, any remaining space at the end to be closed is filled with dunnage such that the cylinder is obstructed from moving inside the first container.
Next, the first container is wrapped with a fiber paper having low thermal conductivity and high heat reflectance properties. The fiber paper is flexible and can be cut to size such that it can be wrapped around the sides of the first container. The top and bottom of the first container are then provided with an end cap cardboard spacer. The first container with the fiber paper wrapped around the sides and with the spacers at the top and bottom is then inserted into a second container. The side walls of the first container are disposed in spaced apart parallel relation to the walls of the second container. The end cap spacer at the top and bottom of the first container provides for positioning of the first container inside the second container, prevents the first container from moving inside the second container, and prevents contact between the first and second container. As an alternative, the fiber paper may be bonded or otherwise attached to the inside surface of the second container.
The second container is preferably coated on its exterior with a flame retardant coating. As an alternative, the second container may also be provided with a flame retardant coating on its interior.
The second container may be provided with endcap spacers and then inserted into a third container, if necessary. The side walls of the second container would be disposed in spaced apart parallel relation to the walls of the third container. Also, as an alternative arrangement, a thermal barrier in the form of fiber paper could be disposed between the second and third containers such as by wrapping the paper around the second container or attaching the paper to the inside of the third container.
Accordingly, multiple containers disposed within each other in spaced apart relation could be provided. The successive containers may also be coated on the exterior or interior surfaces with a flame retardant substance.